Low flow or micro irrigation is a form of irrigation of plants, row crops, trees and shrubs, where the amount of water delivered to the plant is metered into the range of ½ gallon per hour and as high as 28 gallons per hour for bubbler devices and sprayers, depending on the type of soil, type of plant or tree, and the individual requirements of the plant, such as roses that like to be heavily watered, letting the ground dry out between watering. The average plant can absorb approximately 1 gallon per hour through it's root system and the roots need air to aid in this absorption process. Conventional watering systems, such as hose end devices and conventional lawn sprinklers and bubblers, can deliver more than 125 gallons per hour, causing much waste not only of the actual resource of the water but alters the geology, topography and composition of the soils. Excess water usually runs away from the planting area causing erosion, which carries off the valuable top soil and causes damage to the plants as their roots can become exposed and dry out. Runoff water can also carry with it fertilizers and soil nutrients, which can pollute other areas and rob the plant of its food source. Excess watering also causes the leeching of dissolved salts and minerals from the ground and concentrates them where the runoff is collected, often killing whatever vegetation is present due to the high concentrations of salt and heavy metals. Excess water also creates an economic disadvantage as there exist the actual cost of the wasted water and the cost of the power to pump the water from it's source. Many studies support the concept of low volume or micro irrigation for many types of plants and trees, as a benefit to more better plant health and environment, where the returns include better crop yields due to healthier plants and the development of a stable topsoil.
Low volume irrigation is broken down into two main categories; point source devices and wetted area devices. Wetted area devices are most commonly seen as bubblers and sprayers with patterns and sprinklers with rotating or static elements which actually increase the velocity of the water droplets to increase their range. Wetted area devices usually deliver 7 to 28 gallons per hour. Point source devices deliver water to a specific point, such as a dripper, where the amount of water delivered is between ½-4 gallons per hour. A point source device is usually placed along the ground within the dripline of the plant or tree and vary in number depending on the amount of water is needed. Wetted area devices are used on ground covers and between trees to encourage root spread of the tree to the water source.
Topography and climate play a large factor in designing low volume irrigation systems. Hillside applications, especially in the grape growing and citrus growing regions where good land is very valuable and is often not flat, present problems. Point source devices will deliver water only to a specific point limiting coverage and creating runoff as gravity pulls the water away from the plant and may not be able to deliver a sufficient amount of water, and sprinklers will deliver too much water and will cause the erosion effects described supra. Windy conditions also affect micro irrigation when sprinklers and sprayers are used. Due to the size of the droplet produced, which is much smaller than a conventional sprinkler due to the decreased volume of water, wind will blow the spray away from the intended watering area. Usually the spray is directed horizontally along the ground from a device that is placed 1-2 feet above the ground in order to increase the area of the wetted surface. Point source devices are not susceptible to this wind, but may not be able to deliver a sufficient amount of water and will not be able to do so over a wetted area.
Prior art is replete with examples of low volume wetted area devices. In the agricultural and large horticultural applications, most water supply conduits are required to carry vast amounts of water to many locations, usually far from the source of the water, and then there must exist some medium to reduce the large volume of water present to a low volume. There are three main methods of reducing this volume; flow restriction, reduction of aperture size, and intermittent watering.
Flow restriction device are either static or dynamic. A dynamic flow restriction device is detailed in U.S. Pat. No. 4,084,749 to Drori issued on Apr. 18, 1978. Here the volume of water is reduced through the use of a labyrinth which retards the flow of the water. An embodiment to Drori is a spring-biased pressure sensing member whose movement decreases flow in response to pressure differentials. Unfortunately, for this device to function in the range of ½ gallon per hour, the tolerance of manufacturing variables in the many pieces present would be impractical for high volume manufacturing. Also this device would not be able to able to internally cleanse itself as there are many internal corners and narrow passageways where dirt and dissolved solids would accumulate and cause failure. Also due to the friction created by the many turns the water must go through, there is a substantial pressure drop. Other dynamic flow control devices are present in the pressure compensating drippers manufactured by many irrigation companies around the world, where flow rates as low as ½ gallon per hour are common. These drippers are made of polymer materials where a labyrinth is integral to the polymer material which is encased in a rigid body or these drippers have a rigid labyrinth body over which a silicone disk is placed. In either instance, the disk or polymer flexes and seals against the rigid body reducing the amount of flow allowed to pass. These devices however reduce the amount of flow while also reducing the pressure through friction as well, so that the resulting flow is delivered at a de minims amount of pressure. Due to this low pressure and the small openings of the labyrinth, these devices are often prone to clogging through particle and mineral deposits.
The Static flow controls are flexible usually circular pieces that contain a passageway centered therein, said passageway containing beveled sides, whereby the passageway on the top of the flow control, the side facing the water supply, will have a diameter smaller than the diameter of the passageway on the back of the flow control. This flow control flexes causing the passageway to constrict thereby reducing the flow past the flow control device. The size of the hole dictates the amount of flow restricted. This device is marketed by such irrigation companies such as Raindrip Inc. as Flow Control Device Part Number R425C and Hendrickson Bros Inc, Part Number HM-50G, and is disclosed in U.S. Pat. No. 4,492,339 issued to Kreitzberg on Jan. 8, 1985. These devices function well at higher flow volumes but are limited to those flows approximately 6 gallons per hour and above as the size of the hole necessary to create a lower flow causes problems in the manufacturability and functionality of the flow control as well as presenting issues with cleaning and clogging. In this application, which relies on a high velocity stream of fluid, a flow control disk of correct cross-sectional orifice size would not allow for enough velocity.
The restriction of the nozzle size is the principle of the nozzle placed on the garden hose. Water pushed through a smaller orifice increases it velocity or pressure following Boyle's Law. Products that regulate flow through a fixed orifice include one's ordinary lawn sprinklers. By decreasing the size of the orifice, the amount of water is decreased as water is not capable of decreasing in volume as pressure is increased. Thus, only a specific amount of water can go through an orifice irrespective of the amount of pressure behind the water. This also causes a pressure differential between the two sides of the orifice. The restriction of nozzle size is applicable to high flow devices such as lawn sprinklers which are delivering 60-90 gallons per hour or more, but the size of the orifice required to create flows necessary for low volume irrigation is very small. A 0.060″ orifice is still capable of delivering up to 28 gallons per hour at 25 psi, To reach the level of this invention, the size of the orifice would need to be approximately 0.006″ to achieve an output of ½ gallon per hour. An orifice this small will easily be obstructed by the dissolved solids and impurities present in the water, as filtration would generally not be able to remove such small particles. Also after the water is turned off, calcium and other hard minerals are left on the surface of the orifice through evaporation, clogging the nozzle prior to the next operation.
Intermittent watering involves the principle of a uniform discharge of water that is accomplished at predetermined intervals of time. U.S. Pat. Nos. 5,727,733 and 4,955,539 to Ruttenberg and U.S. Pat. No. 5,314,116 to Krauth et al, typify the intermittent style of sprinkler. These devices convert a low flow of water into a high flow of water by using short bursts of water frequently over a period of time, causing a lower volume of water to be expelled over a greater wetted area. It is a basic principle that when a high pressure stream of water is diverted, a smaller water droplet is formed, than if a lower pressure stream of water is diverted. It is also basic in principle that a smaller droplet of water will not travel as far as a larger droplet of water when subjected to a similar pressure that propels them. Water droplets tend to rapidly break down into smaller and smaller droplets as the pressure increases, causing an atomization of the water droplets at higher pressures. It is also basic in principle that a lower flow rate traveling through a particular orifice will travel a shorter distant than a high flow rate. Simply turning the garden faucet from ¼ open to fully open verifies this principle. The wetted area of a 10 gallon per hour sprinkler is smaller than that of a 20 gallon per hour sprinkler normally. And the droplet size of the 10 gallon is smaller as well. These devices work by capturing a flow of water into an elastic casing which expels the water after it reaches a specific pressure. As the water is expelled, the retraction of the elastic casing increases the pressure, hurling the ejected water out of the sprinkler. In this case, if there was a 20 gallon per hour flow input into the device, and the device only ejected the water every 2 seconds and took 4 seconds to fill the casing for the next ejection, than only 10 gallons per hour would be ejected. But because the amount of water ejected would be equivalent of 20 gallons per hour the size of the orifice and the size of the droplet is equivalent to the 20 gallons per hour as well as the wetted area. The user receives the benefit of a larger droplet size which is less effected by climatic conditions. Unfortunately, for these devices to be able to eject large volumes of water, there orifice size must be larger and that invites insects to enter and block the passages. Also due to the need to develop the casing, these products are difficult to manufacture and expensive. U.S. Pat. No. 6,691,739 to Rosenberg issued on Feb. 17, 2004 uses mechanical means to hold the water until a higher pressure is created. This device as designed will not function completely at low flow rates, and due to the narrow size of the passages required for low flow rate, this device is prone to failure with the accumulation of dissolved solids in the water and requires a complex disassembly to clean the device.
Inherent to the functioning of this invention is the elastomeric flow control valve that provides a constant low volume stream of water throughout a pressure gradient. This flow control must be able to adapt to low pressure as well as higher pressure application and provide a constant flow of water. As described supra, reduction of the flow of water must be accomplished in such a manner whereby hard, static surfaces are avoided to prevent clogging and mis-application of the water. This elastomeric flow control valve must be capable of purging itself at low pressures which will discharge any impediments out of it's flow passages during this purging process. This purging must be accompanied with a sufficiently large diameter orifice sized to eliminate those impediments that would clog the flow paths of the device. This self-cleaning action is desirable as filtration in large field applications are not capable of trapping such small sediment that would otherwise clog static devices. The elastomeric flow control is capable of possessing a larger flow path than would be found in static flow control devices as this flow path reduces as the pressure increases. The flow restriction side of this device is shaped as a bill of a duck with a slot embossed into the interior of one side of the duckbill. As pressure increases, the flow path is restricted and the fluid that is allowed to pass through this slot is in the character of a high velocity stream of fluid, jetting out of the flow control device at the desired amount of flow. There is also a purging action as at starting pressure the arching flow path is large allowing for trapped particles to be flushed through the large orifice and in the presence of higher pressures, those above 2-3 psi, the flow path flexes due to its construction containing elastrometric materials, and reduces the amount of water flowing into the larger orifice at the regulated amount. The major benefit of this style of flow control device is that the amount of flow is limited by the flexing of the device but does not completely reduce the pressure to a minimalist flow. Other manufactures have developed flow regulators that use these elastomeric flow control devices in higher flow rates, such as the Acu-Flo device by Wade Rain Micro-irrigation which functions in-line with feeder tubing and low volume sprinklers. These elastomeric flow control devices have been used at the junction of the supply tubing and the feeder line such as disclosed in U.S. Pat. No. 4,869,432 issued to Christy on Sep. 26, 1989. Both of these applications use elastomeric flow control devices but the flow rates of these devices is rated at 6 gallons per hour and higher and these devices have wetted areas of 6 feet of diameter and greater. Emphasis has been on low volumes over increasingly larger wetted areas. This invention uses lower flow rates than previously had been used in sprinkler applications. Another usage of this elastomeric flow control device has been in lower volume point source devices. U.S. Pat. No. 4,113,180 issued to Christy et al on Sep. 12, 1978 discloses the use of this style of device but teaches it's use in low flow applications in point source devices where the pressure is reduced to a deminimus amount due to a pooling of the output of the elastomeric control valve.
Prior art has only used the flow control characteristics of this valve. Prior art has not used the jetting characteristic of the elastomeric flow control valve. A characteristic of this valve is that the flow path is restricted thus small amounts of flow are expelled at high velocities as the pressure on the input side is much greater than is present at the outlet side. This invention uses this jet of water and changes it's direction gently to produce the desired results. This has not been accomplished nor taught by the prior art. It would be advantageous to develop a spray head that incorporates a flow control device that is integral to the spray head itself. This would reduce the extra tubing, costs and labor associated with installation flow controls separate from the spray heads.
It would be advantageous to have very low volumes of water to be sprayed over a small wetted area, and the current devices are not capable of performing such a need. The prior art either decreases the flow rate by also decreasing the pressure or does not decrease the flow rate low enough with sufficient pressures.
The present invention is a device that when attached to a pressurized conduit of fluid is capable of regulating the amount of fluid flow irrespective of reasonable pressure gradients and deliver that fluid at a constant low delivery rate of less than 2 gallons per hour over a small contiguous wetted area.
It is an object of the present invention to incorporate into a single device the benefits of point source delivery of water at a delivery rate of less than 2 gallon per hour with an increased amount of wetted area, up to 8 square feet preferably at ½ of a gallon per hour.
It is an object of the present invention to be able to deliver fluid at a very low rate consistently through varying pressure gradients while maintaining the ability of self-cleanability and containing sufficiently sized orifices that can accommodate large particulate matter.
It is an object of this present invention to be able to deliver this fluid in different patterns of distribution at low flow rates through varying pressure gradients while maintaining an uniform spray pattern with uniform size of water droplets.
It is an object of this invention to be able to adapt this technology into a variety of situations whereby this invention is able to be used for point source irrigation applications and other agricultural applications such as frost protection, bedding plants or plant or evaporative cooling.